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kmd188 07-22-2012 08:00 AM

Smoking switch through the ground?
Hi, so I recently replaced a light switch that controls one light fixture for the back porch. EVerything was wired correctly and the switch worked. One night while in the kitchen next to the room I heard a pop and the lights flickered. I quickly ran over and found nothing wrong and no breakers were tripped. A couple of days later I smelled something burning and noticed that the wall to the left of the wall plate was slightly charred. I removed the plate and switch to find the switch (brand new Lutron) was charred on the left side at the ground wire. Does anyone know what this means? I'm assuming the circuit jumped, but does it make sense that the ground connector was the source of the smoking? I have the switch removed and all the wires nutted and taped off for now. I'm kind of hesitant to put a new switch in if there is a problem. Sorry for the lengthy post and thanks for the responses.

J. V. 07-22-2012 10:52 AM

Remove the switch and inspect all the wires present. It is a bad connection to the switch. It is a loose wire nut connection or you compromised the insulation on the wire or wires when doing the work. Over the time of the installation and the time it popped, the loose/bad connection got hot. This what we call a "high resistance" connection. If this is on an AFCI breaker, it should have tripped. If it is on a regular/typical circuit breaker this is why it did not trip.
This causes fires and that is why the AFCI was introduced and subsequently required in certain/most rooms in the home.

Edit: Here I found this on a pro site.

The Glowing Connection

The glowing connection usually begins its life as an intermittent connection, or a series
arc. But then something very strange happens. The localized heating caused by the series
arc makes the connected metals begin to oxidize. Once the contact points are oxidized,
electrical resistance begins to increase. This increase in resistance, because it is
in series
with the normal current flow, causes resistance heating just like in an electric heater. The
heating that occurs is very localized, but it begins to cause an alloying of the dissimilar
metals. These alloys have additional, and unexpected, electrical properties. That is, they
semiconductors, and behave in a non-linear fashion to electric current flow. Because
of this non-linear behavior, heating can occur at very low currents such as those drawn
by a "wall wart" type battery charger or AC adapter. A glowing connection may take
hours, days or years to develop but once it has any flickering of lights or intermittent
behavior of electrical devices ceases. Instead, a very low voltage drop occurs (usually 2
volts or so), even when relatively high current electrical loads are in use. Because of this
small voltage drop, incorrect behavior of the load seldom occurs, and so it does not
attract the attention of the user or building occupant.

Julius793 07-22-2012 10:54 AM

take some picture and post them that may help

MisterZ 07-22-2012 01:20 PM

Is the switch bo metal? If yes, consider swapping it out for a single gang plastic one.
This could have been a number of things. Use a volt meter to ensure there is no current on the neutral or ground wires.
Bad insulation could be a problem too. Is this old fabric coated wire? They can be repaired with shrink wrap, but i would replace it if you have this.
Or, it could just be a faulty switch. Check everything.

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